U.S. patent number 10,249,519 [Application Number 15/420,134] was granted by the patent office on 2019-04-02 for light-irradiation heat treatment apparatus.
This patent grant is currently assigned to SCREEN Holdings Co., Ltd.. The grantee listed for this patent is SCREEN Holdings Co., Ltd.. Invention is credited to Makoto Abe.
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United States Patent |
10,249,519 |
Abe |
April 2, 2019 |
Light-irradiation heat treatment apparatus
Abstract
A semiconductor wafer held by a holder within a chamber is
irradiated and heated with halogen light emitted from multiple
halogen lamps. A cylindrical louver made of opaque quartz and a
light-shielding member of a ring shape having a cut-out portion are
provided between the halogen lamps and the semiconductor wafer.
When the semiconductor wafer is heated with the light emitted from
the halogen lamps, a shadow region will appear in the semiconductor
wafer as a result of the louver blocking off the emitted light.
However, in the presence of the cut-out portion of the
light-shielding member, the light emitted from the halogen lamps
will reach the shadow region through the cut-out portion. This
configuration allows the shadow region to be heated in the same
manner as the other regions, and accordingly will help make uniform
the in-plane temperature distribution of the semiconductor wafer
during light irradiation heating.
Inventors: |
Abe; Makoto (Kyoto,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
SCREEN Holdings Co., Ltd. |
Kyoto |
N/A |
JP |
|
|
Assignee: |
SCREEN Holdings Co., Ltd.
(Kyoto, JP)
|
Family
ID: |
59630156 |
Appl.
No.: |
15/420,134 |
Filed: |
January 31, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20170243771 A1 |
Aug 24, 2017 |
|
Foreign Application Priority Data
|
|
|
|
|
Feb 24, 2016 [JP] |
|
|
2016-032733 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
21/67115 (20130101); H05B 3/0047 (20130101) |
Current International
Class: |
F26B
3/30 (20060101); F26B 19/00 (20060101); H01L
21/67 (20060101); H05B 3/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
|
60-258928 |
|
Dec 1985 |
|
JP |
|
2005-527972 |
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Sep 2005 |
|
JP |
|
2012-174879 |
|
Sep 2012 |
|
JP |
|
1250587 |
|
Mar 2006 |
|
TW |
|
201344740 |
|
Nov 2013 |
|
TW |
|
Other References
Taiwan Decision of Grant dated Aug. 29 2017 for Taiwan Application
No. 106100111 and Taiwan search report with English translation
thereof. cited by applicant.
|
Primary Examiner: Campbell; Thor S
Attorney, Agent or Firm: Ostrolenk Faber LLP
Claims
What is claimed is:
1. A heat treatment apparatus for heating a disk-shaped substrate
by irradiating the substrate with light, comprising: a chamber that
houses a substrate; a holder that holds said substrate in said
chamber; a light irradiation part in which a plurality of
rod-shaped lamps are arranged in a light source region that is
larger than a major surface of said substrate held by said holder
and that faces the major surface; a cylindrical louver that is
provided between said light irradiation part and said holder, with
a central axis of said louver passing through a center of said
substrate, and that is impervious to light emitted from said light
irradiation part, and an outer diameter of said louver being
smaller than said light source region; and a light-shielding member
that is provided between said light irradiation part and said
holder and that is impervious to the light emitted from said light
irradiation part, wherein said light-shielding member has a cut-out
portion that allows light to reach a region of said substrate that
is shielded from the light emitted from said light irradiation part
by said louver.
2. The heat treatment apparatus according to claim 1, wherein said
light-shielding member includes: a light-shielding ring having said
cut-out portion; and a light-shielding piece arranged inside said
light-shielding ring.
3. A heat treatment apparatus for heating a disk-shaped substrate
by irradiating the substrate with light, comprising: a chamber that
houses a substrate; a holder that holds said substrate within said
chamber; a light irradiation part in which a plurality of
rod-shaped lamps are arranged in a light source region that is
larger than a major surface of said substrate held by said holder
and that faces the major surface; a cylindrical louver that is
provided between said light irradiation part and said holder, with
a central axis of said louver passing through a center of said
substrate, and that is impervious to light emitted from said light
irradiation part, and an outer diameter of said louver being
smaller than said light source region; and a light-shielding member
that is provided between said light irradiation part and said
holder and that is impervious to the light emitted from said light
irradiation part, wherein part of said light-shielding member is
made of a transparent member to allows light to reach a region of
said substrate that is shielded from the light emitted from said
light irradiation part by said louver.
4. The heat treatment apparatus according to claim 3, wherein said
part of said light-shielding member is made of transparent quartz,
and a remaining part of said light-shielding member is made of
opaque quartz.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a heat treatment apparatus for
heating a sheet precision electronic substrate (hereinafter, simply
referred to as a "substrate"), such as a disk-shaped semiconductor
wafer, by irradiating the substrate with light.
Description of the Background Art
In the process of manufacturing a semiconductor device, the
introduction of impurities is an essential step for forming pn
junctions in a semiconductor wafer. It is common at present to
introduce impurities by ion implantation and subsequent annealing.
Ion implantation is a technique for physically doping a
semiconductor wafer with impurities by ionizing impurity elements,
such as boron (B), arsenic (As), or phosphorus (P), and causing the
impurity elements to collide with the semiconductor wafer with a
high acceleration voltage. The doped impurities are activated by
annealing. At this time, if the annealing time is about several
seconds or longer, the doped impurities may be diffused deeply by
heat, and as a result, the junction depth may become too deeper
than required and compromise the formation of a good device.
In view of this, flash-lamp annealing (FLA) is recently receiving
attention as an annealing technique for heating semiconductor
wafers in an extremely short time. Flash-lamp annealing is a heat
treatment technique using xenon flash lamps (hereinafter, sometimes
simply referred to as "flash lamps") to irradiate a surface of an
impurity-doped semiconductor wafer with flash light and raise the
temperature of only the surface of the semiconductor wafer in an
extremely short time (e.g., several milliseconds or less).
The radiation spectral distribution of xenon flash lamps ranges
from ultraviolet to near-infrared regions, with the xenon flash
lamps having shorter wavelengths than conventional halogen lamps,
and approximately coincides with the fundamental absorption band of
silicon semiconductor wafers. Thus, when xenon flash lamps emit
flash light to a semiconductor wafer, less light will pass through
the semiconductor wafer and accordingly the temperature of the
semiconductor wafer will rise quickly. It is also known that
extremely short-time application of flash light, such as several
milliseconds or less, will only selectively increase the
temperature in the vicinity of the surface of the semiconductor
wafer. Such an extremely short-time temperature rise caused by the
xenon flash lamps will only activate impurities without deeply
diffusing the impurities.
Examples of the heat treatment apparatus using xenon flash lamps
include those disclosed in U.S. Pat. No. 4,698,486 and US
2003/0183612, in which desired heat treatment is achieved by a
combination of pulsed light-emitting lamps, such as flash lamps,
that are arranged on the front side of a semiconductor wafer and
continuous lighting lamps, such as halogen lamps, that are arranged
on the rear side of the semiconductor wafer. In the heat treatment
apparatuses disclosed in U.S. Pat. No. 4,698,486 and US
2003/0183612, a semiconductor wafer is preheated to a certain
degree of temperature by, for example, halogen lamps and then
heated to a desired processing temperature by pulse heating using
flash lamps.
Preheating using the halogen lamps, as disclosed in U.S. Pat. No.
4,698,486 and US 2003/0183612, has a processing advantage that the
semiconductor wafer will be preheated to a relatively high
preheating temperature in a short time, but at the same time, it
may more likely cause a problem that the peripheral portion of the
semiconductor wafer will have a lower temperature than the central
portion. Conceivable causes of this uneven temperature distribution
include heat radiation from the peripheral portion of the
semiconductor wafer, and heat conduction into a relatively
low-temperature quartz susceptor from the peripheral portion of the
semiconductor wafer. In order to address this problem, Japanese
Patent Application Laid-Open No 2012-174879 proposes to install a
cylindrical louver made of a semitransparent material between
halogen lamps and a semiconductor wafer in order to make uniform
the in-plane temperature distribution of the semiconductor wafer
during preheating.
The presence of the louver, as proposed in Japanese Patent
Application Laid-Open No. 2012-174879, ameliorates the problem of a
temperature drop in the peripheral portion of the semiconductor
wafer, but a new problem arises in that the presence of the louver
conversely increases the temperature in a region of a semiconductor
wafer that is slightly inward of the peripheral portion of the
semiconductor wafer.
SUMMARY OF THE INVENTION
The present invention is directed to a heat treatment apparatus for
heating a disk-shaped substrate by irradiating the substrate with
light.
According to an aspect of the present invention, the heat treatment
apparatus includes a chamber that houses a substrate, a holder that
holds the substrate in the chamber, a light irradiation part in
which a plurality of rod-shaped lamps are arranged in a light
source region that is larger than a major surface of the substrate
held by the holder and that faces the major surface, a cylindrical
louver that is provided between the light irradiation part and the
holder, with a central axis of the louver passing through a center
of the substrate, and that is impervious to light emitted from the
light irradiation part, and a light-shielding member that is
provided between the light irradiation part and the holder and that
is impervious to the light emitted from the light irradiation part.
The light-shielding member has a cut-out portion that allows light
to reach a region of the substrate that is shielded from the light
emitted from the light irradiation part by the louver.
This configuration allows light to reach and heat this region in
the same manner as the other regions and therefore will help make
uniform the in-plane temperature distribution of the substrate.
According to another aspect of the present invention, the heat
treatment apparatus includes a chamber that houses a substrate, a
holder that holds the substrate within the chamber, a light
irradiation part in which a plurality of rod-shaped lamps are
arranged in a light source region that is larger than a major
surface of the substrate held by the holder and that faces the
major surface, a cylindrical louver that is provided between the
light irradiation part and the holder, with a central axis of the
louver passing through a center of the substrate, and that is
impervious to light emitted from the light irradiation part, and a
light-shielding member that is provided between the light
irradiation part and the holder and that is impervious to the light
emitted from the light irradiation part. Part of the
light-shielding member is made of a transparent member to allows
light to reach a region of the substrate that is shielded from the
light emitted from the light irradiation part by the louver.
This configuration allows light to reach and heat this region in
the same manner as the other regions and therefore will help make
uniform the in-plane temperature distribution of the substrate.
Thus, an object of the present invention is to make uniform the
in-plane temperature distribution of a substrate.
These and other objects, features, aspects and advantages of the
present invention will become more apparent from the following
detailed description of the present invention when taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal cross-sectional view of a heat treatment
apparatus according to the present invention;
FIG. 2 is a perspective view of the overall external appearance of
a holder;
FIG. 3 is a plan view of a susceptor;
FIG. 4 is a cross-sectional view of the susceptor;
FIG. 5 is a plan view of a transfer mechanism;
FIG. 6 is a side view of the transfer mechanism;
FIG. 7 is a plan view illustrating the arrangement of multiple
halogen lamps;
FIG. 8 is a perspective view of a louver;
FIG. 9 is a perspective view of the overall external appearance of
the louver and a light-shielding member according to a first
preferred embodiment;
FIG. 10 is a perspective view of the overall external appearance of
a cylindrical louver including a perfect ring-shaped
light-shielding member;
FIG. 11 illustrates how light is shielded by the structure in FIG.
10;
FIG. 12 illustrates how optical paths are adjusted by the louver
and the light-shielding member according to the first preferred
embodiment;
FIG. 13 is a plan view of a light-shielding member according to a
second preferred embodiment;
FIG. 14 is a plan view of a light-shielding member according to a
third preferred embodiment;
FIG. 15 is a plan view of a light-shielding member according to a
fourth preferred embodiment; and
FIG. 16 illustrates the in-plane temperature distribution of the
semiconductor wafer in the presence of only a louver.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, preferred embodiments of the present invention will be
described in detail with reference to the drawings.
First Preferred Embodiment
FIG. 1 is a longitudinal cross-sectional view of a configuration of
a heat treatment apparatus 1 according to the present invention.
The heat treatment apparatus 1 of the present preferred embodiment
is a flash-lamp annealing apparatus for heating a disk-shaped
semiconductor wafer W, which is a substrate, by irradiating the
semiconductor wafer W with flash light. The size of the
semiconductor wafer W to be processed is not particularly limited
and may have a diameter of, for example, .PHI.300 mm or .PHI.450 mm
(in the present preferred embodiment, .PHI.300 mm). The
semiconductor wafer W is doped with impurities before being
conveyed into the heat treatment apparatus 1, and the doped
impurities are activated by heat treatment performed by the heat
treatment apparatus 1. For easy understanding of drawings, the
dimensions of each constituent element and the number of
constituent elements in FIG. 1 and subsequent drawings may be
exaggerated or simplified as necessary.
The heat treatment apparatus 1 includes a chamber 6 that houses the
semiconductor wafer W, a flash heater 5 that includes multiple
built-in flash lamps FL, and a halogen heater 4 that includes
multiple built-in halogen lamps HL. The flash heater 5 is located
above the chamber 6, and the halogen heater 4 is located below the
chamber 6. A louver 21 and a light-shielding member 25 are provided
between the halogen heater 4 and the chamber 6. The heat treatment
apparatus 1 further includes, within the chamber 6, a holder 7 that
holds the semiconductor wafer W in a horizontal position and a
transfer mechanism 10 for transferring the semiconductor wafer W
between the holder 7 and the outside of the heat treatment
apparatus 1. The heat treatment apparatus 1 further includes a
controller 3 that controls operating mechanisms provided in the
halogen heater 4, the flash heater 5, and the chamber 6 to perform
the heat treatment of the semiconductor wafer W.
The chamber 6 is configured by mounting quartz chamber windows on
the top and bottom of a tubular chamber side portion 61. The
chamber side portion 61 has a roughly tubular shape that is open at
the top and the bottom, the opening at the top being equipped with
and closed by an upper chamber window 63 and the opening at the
bottom being equipped with and closed by a lower chamber window 64.
The upper chamber window 63, which forms the ceiling of the chamber
6, is a disk-shaped member made of quartz and functions as a quartz
window that allows the flash light emitted from the flash heater 5
to pass through it into the chamber 6. The lower chamber window 64,
which forms the floor of the chamber 6, is also a disk-shaped
member made of quartz and functions as a quartz window that allows
the light emitted from the halogen heater 4 to pass through it into
the chamber 6.
A reflection ring 68 is mounted on the upper part of the inner wall
surface of the chamber side portion 61, and a reflection ring 69 is
mounted on the lower part thereof. Both of the reflection rings 68
and 69 have a ring shape. The upper reflection ring 68 is mounted
by being fitted from above the chamber side portion 61. The lower
reflection ring 69 is mounted by being fitted from below the
chamber side portion 61 and fastened with screws (not shown). That
is, the reflection rings 68 and 69 are both removably mounted on
the chamber side portion 61. The chamber 6 has an inner space that
is surrounded by the upper chamber window 63, the lower chamber
window 64, the chamber side portion 61, and the reflection rings 68
and 69 and defined as a heat treatment space 65.
The presence of the reflection rings 68 and 69 on the chamber side
portion 61 generates a recessed portion 62 in the inner wall
surface of the chamber 6. That is, the recessed portion 62 is
surrounded by a central portion of the inner wall surface of the
chamber side portion 61 on which the reflection rings 68 and 69 are
not mounted, the lower end surface of the reflection ring 68, and
the upper end surface of the reflection ring 69. The recessed
portion 62 has a ring shape extending in a horizontal direction
along the inner wall surface of the chamber 6, and surrounds the
holder 7 that holds the semiconductor wafer W.
The chamber side portion 61 and the reflection rings 68 and 69 are
each made of a metal material (e.g., stainless steel) having
excellent strength and heat resistance. The inner circumferential
surfaces of the reflection rings 68 and 69 are mirror-finished by
electrolytic nickel plating.
The chamber side portion 61 has a transport opening (throat) 66
through which the semiconductor wafer W is transported into and out
of the chamber 6. The transport opening 66 is openable and closable
by a gate valve 185. The transport opening 66 is communicatively
connected to the outer circumferential surface of the recessed
portion 62. Thus, when the gate valve 185 opens the transport
opening 66, the semiconductor wafer W can be transported into and
out of the heat treatment space 65 from the transport opening 66
through the recessed portion 62. When the gate valve 185 closes the
transport opening 66, the heat treatment space 65 in the chamber 6
becomes an enclosed space.
The upper part of the inner wall of the chamber 6 has a gas supply
port 81 through which a process gas (in the present preferred
embodiment, nitrogen gas (N.sub.2)) is supplied to the heat
treatment space 65. The gas supply port 81 is located at a position
above the recessed portion 62 and may be provided in the reflection
ring 68. The gas supply port 81 is communicatively connected to a
gas supply pipe 83 through a buffer space 82 that is formed in a
ring shape inside the side wall of the chamber 6. The gas supply
pipe 83 is connected to a nitrogen gas supply source 85. A valve 84
is interposed in the path of the gas supply pipe 83. When the valve
84 is open, a nitrogen gas is supplied from the gas supply source
85 to the buffer space 82. The nitrogen gas flowing into the buffer
space 82 flows throughout the buffer space 82, which has lower
fluid resistance than the gas supply port 81, and is supplied from
the gas supply port 81 into the heat treatment space 65. Note that
the process gas is not limited to a nitrogen gas, and may be an
inert gas such as argon (Ar) or helium (He), or a reactive gas such
as oxygen (O.sub.2), hydrogen (H.sub.2), chlorine (Cl.sub.2),
hydrogen chloride (HCl), ozone (O.sub.3), or ammonia
(NH.sub.3).
On the other hand, the lower part of the inner wall of the chamber
6 has a gas exhaust port 86 from which the gas in the heat
treatment space 65 is exhausted. The gas exhaust port 86 is located
at a position below the recessed portion 62 and may be provided in
the reflection ring 69. The gas exhaust port 86 is communicatively
connected to a gas exhaust pipe 88 through a buffer space 87 that
is formed in a ring shape inside the side wall of the chamber 6.
The gas exhaust pipe 88 is connected to an exhaust part 190. A
valve 89 is interposed in the path of the gas exhaust pipe 88. When
the valve 89 is open, the gas in the heat treatment space 65 is
exhausted from the gas exhaust port 86 through the buffer space 87
to the gas exhaust pipe 88. Alternatively, multiple gas supply
ports 81 and multiple gas exhaust ports 86 may be provided in the
direction along the circumference of the chamber 6, or the gas
supply port 81 and the gas exhaust port 86 may be slit-shaped. The
nitrogen gas supply source 85 and the exhaust part 190 may be
mechanisms provided in the heat treatment apparatus 1, or may be
utilities in a factory where the heat treatment apparatus 1 is
installed.
One end of the transport opening 66 is connected to a gas exhaust
pipe 191 from which the gas in the heat treatment space 65 is
exhausted. The gas exhaust pipe 191 is connected via a valve 192 to
the exhaust part 190. When the valve 192 is open, the gas in the
chamber 6 is exhausted from the transport opening 66.
FIG. 2 is a perspective view of the overall external appearance of
the holder 7. The holder 7 is constituted by a base ring 71,
connecting parts 72, and a susceptor 74. The base ring 71, the
connecting parts 72, and the susceptor 74 are all made of quartz.
That is, the holder 7 as a whole is made of quartz.
The base ring 71 is a quartz member having an arc shape that is a
ring shape having a missing portion. The missing portion is
provided in order to avoid interference between the base ring 71
and transfer arms 11 of the transfer mechanism 10, which will be
described later. The base ring 71 is placed on the bottom surface
of the recessed portion 62 and thereby supported by the wall
surface of the chamber 6 (see FIG. 1). The upper surface of the
base ring 71 has the multiple (in the present preferred embodiment,
four) upright connecting parts 72 arranged along the circumference
of the base ring 71. The connecting parts 72 are also quartz
members and fixedly attached to the base ring 71 by welding.
The susceptor 74 is supported by the four connecting parts 72
provided on the base ring 71. FIG. 3 is a plan view of the
susceptor 74. FIG. 4 is a cross-sectional view of the susceptor 74.
The susceptor 74 includes a holding plate 75, a guide ring 76, and
multiple substrate support pins 77. The holding plate 75 is a
substantially circular flat plate-like member made of quartz. The
diameter of the holding plate 75 is greater diameter than the
diameter of the semiconductor wafer W. That is, the holding plate
75 has a greater plane size than the semiconductor wafer W.
The guide ring 76 is provided on the periphery of the upper surface
of the holding plate 75. The guide ring 76 is a ring-shaped member
having a greater inner diameter than the diameter of the
semiconductor wafer W. For example, when the semiconductor wafer W
has a diameter of .PHI.300 mm, the inner diameter of the guide ring
76 is .PHI.320 mm. The inner periphery of the guide ring 76 is a
tapered surface that tapers upward from the holding plate 75. The
guide ring 76 is made of quartz similar to that of the holding
plate 75. The guide ring 76 may be welded to the upper surface of
the holding plate 75, or may be fixed to the holding plate 75 with
pins that are processed separately or by other means.
Alternatively, the holding plate 75 and the guide ring 76 may be
processed as an integral member.
A region of the upper surface of the holding plate 75 that is
inward of the guide ring 76 serves as a flat plate-like holding
surface 75a on which the semiconductor wafer W is held. The
multiple substrate support pins 77 are provided upright on the
holding surface 75a of the holding plate 75. In the present
preferred embodiment, 12 substrate support pins 77 in total are
provided upright at an interval of 30 degrees along the
circumference of a circle that is concentric with the outer
circumferential circle of the holding surface 75a (or the inner
circumferential circle of the guide ring 76). The diameter of the
circle along which the 12 substrate support pins 77 are provided
(i.e., the distance between opposing substrate support pins 77) is
smaller than the diameter of the semiconductor wafer W, and may be
in the range of .PHI.270 mm to .PHI.280 mm (in the present
preferred embodiment, .PHI.280 mm) when the semiconductor wafer W
has a diameter of .PHI.300 mm. Each substrate support pin 77 is
made of quartz. The multiple substrate support pins 77 may be
provided by welding on the upper surface of the holding plate 75,
or may be processed integrally with the holding plate 75.
Referring back to FIG. 2, the four connecting parts 72 provided
upright on the base ring 71 and the peripheral portion of the
holding plate 75 of the susceptor 74 are fixedly attached to each
other by welding. That is, the susceptor 74 and the base ring 71
are fixedly coupled to each other by the connecting parts 72. The
base ring 71 of the holder 7 is supported by the wall surface of
the chamber 6, and thereby the holder 7 is mounted on the chamber
6. With the holder 7 mounted on the chamber 6, the holding plate 75
of the susceptor 74 is held in a horizontal position (position at
which the normal coincides with the vertical direction). That is,
the holding surface 75a of the holding plate 75 becomes
horizontal.
The semiconductor wafer W transported into the chamber 6 is placed
and held in a horizontal position on the susceptor 74 of the holder
7 mounted on the chamber 6. At this time, the semiconductor wafer W
is supported by the 12 substrate support pins 77 provided upright
on the holding plate 75 and is held by the susceptor 74. To be
exact, the upper ends of the 12 substrate support pins 77 come in
contact with the lower surface of the semiconductor wafer W and
support the semiconductor wafer W. Since the 12 substrate support
pins 77 have the same height (the same distance from the upper ends
of the substrate support pins 77 to the holding surface 75a of the
holding plate 75), they can support the semiconductor wafer W in a
horizontal position.
The semiconductor wafer W is supported by the multiple substrate
support pins 77, with a predetermined spacing from the holding
surface 75a of the holding plate 75. The guide ring 76 has a
thickness greater than the height of the substrate support pins 77.
Thus, the presence of the guide ring 76 prevents the semiconductor
wafer W supported by the multiple substrate support pins 77 from
being misaligned in the horizontal direction.
As illustrated in FIGS. 2 and 3, the holding plate 75 of the
susceptor 74 has a vertically penetrating opening 78. The opening
78 is provided to allow a radiation thermometer 120 (see FIG. 1) to
receive radiation light (infrared light) radiated from the
underside of the semiconductor wafer W held by the susceptor 74.
That is, the radiation thermometer 120 receives the light radiated
from the underside of the semiconductor wafer W held by the
susceptor 74 through the opening 78, and the temperature of the
semiconductor wafer W is measured with a separate-type detector.
The holding plate 75 of the susceptor 74 further has four through
holes 79 that allow lift pins 12 of the transfer mechanism 10,
which will be described later, to pass through them for transfer of
the semiconductor wafer W.
FIG. 5 is a plan view of the transfer mechanism 10. FIG. 6 is a
side view of the transfer mechanism 10. The transfer mechanism 10
includes two transfer arms 11. The transfer arms 11 have an arc
shape that extends along the substantially ring-shaped recessed
portion 62. Each transfer arm 11 has two upright lift pins 12 and
is pivotable by a horizontal movement mechanism 13. The horizontal
movement mechanism 13 horizontally moves the pair of transfer arms
11 between a transfer operation position (position indicated by the
solid line in FIG. 5) at which the semiconductor wafer W is
transferred to the holder 7 and a retracted position (position
indicated by the dashed double-dotted line in FIG. 5) at which the
transfer arms 11 do not overlap with the semiconductor wafer W held
by the holder 7 in a plan view. The horizontal movement mechanism
13 may be a mechanism for pivoting each transfer arm 11 separately
by an individual motor, or may be a mechanism for using a link
mechanism to pivot the pair of transfer arms 11 in conjunction with
each other by a single motor.
The pair of transfer arms 11 are also movable up and down along
with the horizontal movement mechanism 13 by an elevating mechanism
14. When the elevating mechanism 14 moves the pair of transfer arms
11 upward at the transfer operation position, the four lift pins 12
in total pass through the through holes 79 (see FIGS. 2 and 3) of
the susceptor 74 so that the upper ends of the lift pins 12
protrude from the upper surface of the susceptor 74. On the other
hand, when the elevating mechanism 14 moves the pair of transfer
arms 11 downward at the transfer operation position to pull the
lift pins 12 out of the through holes 79 and the horizontal
movement mechanism 13 moves the pair of transfer arms 11 so as to
open the transfer arms 11, each transfer arm 11 moves to its
retracted position. The retracted positions of the pair of transfer
arms 11 are directly above the base ring 71 of the holder 7. Since
the base ring 71 is placed on the bottom surface of the recessed
portion 62, the retracted positions of the transfer arms 11 are
inside the recessed portion 62. Note that an exhaust mechanism (not
shown) is also provided in the vicinity of an area where the
driving part (the horizontal movement mechanism 13 and the
elevating mechanism 14) of the transfer mechanism 10 is provided,
in order to allow the atmosphere around the driving part of the
transfer mechanism 10 to be exhausted to the outside of the chamber
6.
Referring back to FIG. 1, the flash heater 5 provided above the
chamber 6 includes, within a casing 51, a light source that
includes multiple (in the present preferred embodiment, 30) xenon
flash lamps FL, and a reflector 52 that is provided to cover the
top of the light source. The casing 51 of the flash heater 5 also
has a lamp-light radiating window 53 mounted on the bottom. The
lamp-light radiating window 53, which forms the floor of the flash
heater 5, is a plate-like quartz window made of quartz. Since the
flash heater 5 is located above the chamber 6, the lamp-light
radiating window 53 faces the upper chamber window 63. The flash
lamps FL emit flash light from above the chamber 6 to the heat
treatment space 65 through the lamp light irradiation window 53 and
the upper chamber window 63.
The multiple flash lamps FL are rod-shaped lamps, each having an
elongated cylindrical shape, and are arrayed in a plane such that
their longitudinal directions are parallel to one another along the
major surface of the semiconductor wafer W held by the holder 7
(i.e., in the horizontal direction). Thus, a plane formed by the
array of the flash lamps FL is also a horizontal plane.
The xenon flash lamps FL each include a rod-shaped glass tube
(discharge tube) and a trigger electrode provided on the outer
circumferential surface of the glass tube, the glass tube
containing a xenon gas sealed therein and including an anode and a
cathode that are disposed at opposite ends of the glass tube and
connected to a capacitor. Since the xenon gas serves electrically
as an insulator, no electricity will flow within the glass tube
under normal conditions even if the capacitor stores electric
charge. However, if an electrical breakdown has occurred due to the
application of a high voltage to the trigger electrode, the
electricity stored in the capacitor will instantaneously flow
within the glass tube, and light will be emitted by the excitation
of xenon atoms or molecules at that time. These xenon flash lamps
FL have the properties of being able to apply extremely intense
light, as compared with light sources for continuous lighting such
as the halogen lamps HL, because the electrostatic energy stored in
advance in the capacitor is converted into an extremely short
optical pulse of 0.1 to 100 milliseconds. That is, the flash lamps
FL are pulsed light-emitting lamps that emit light instantaneously
for an extremely short time (e.g., less than one second). Note that
the light emission time of the flash lamps FL may be adjusted by
using the coil constant of a lamp source that supplies power to the
flash lamps FL.
The reflector 52 is provided above the multiple flash lamps FL to
cover the whole of the flash lamps FL. The reflector 52 has a basic
function of reflecting the flash light emitted from the multiple
flash lamps FL toward the heat treatment space 65. The reflector 52
is made of an aluminum alloy plate, and the surface (surface facing
the flash lamps FL) of the reflector 52 is roughened by
blasting.
The halogen heater 4 located below the chamber 6 includes the
multiple (in the present preferred embodiment, 40) build-in halogen
lamps HL within a casing 41. The halogen heater 4 is a light
irradiation part that causes the multiple halogen lamps HL to emit
light from the underside of the chamber 6 to the heat treatment
space 65 through the lower chamber window 64 and to heat the
semiconductor wafer W.
FIG. 7 is a plan view illustrating the arrangement of the multiple
halogen lamps HL. In the first preferred embodiment, the multiple
halogen lamps HL are arranged in a region that is larger than the
main surface of the disk-shaped semiconductor wafer W held by the
holder 7 (i.e., 300-mm diameter circle). The multiple halogen lamps
HL are also arranged in a light source region that faces the lower
main surface of the semiconductor wafer W.
As illustrated in FIGS. 1 and 7, the 40 halogen lamps HL are
divided into and arranged in upper and lower rows in the first
preferred embodiment. The upper row, which is closer to the holder
7, includes an array of 20 halogen lamps HL, and the lower row,
which is further to the holder 7 than the upper row, includes an
array of 20 halogen lamps HL. Each halogen lamp HL is a rod-shaped
lamp having an elongated cylindrical shape. The 20 halogen lamps HL
in each of the upper and lower rows are arranged such that their
longitudinal directions are parallel to one another along the major
surface of the semiconductor wafer W held by the holder 7 (i.e., in
the horizontal direction). Thus, a plane formed by the array of the
halogen lamps HL in the upper row and a plane formed by the array
of the halogen lamps HL in the lower row are both horizontal
planes.
As illustrated in FIG. 7, a lamp group of the upper row of halogen
lamps HL and a lamp group of the lower row of halogen lamps HL are
arranged so as to intersect each other in a grid-like pattern. That
is, the 40 halogen lamps HL in total are arranged such that the
direction along the lengths of the upper row of 20 halogen lamps HL
and the direction along the lengths of the lower row of 20 halogen
lamps HL are orthogonal to each other.
The halogen lamps HL are filament-type light sources that make the
filament disposed in the glass tube incandescent and emit light by
applying current to the filament. The glass tube contains a gas
that is produced by introducing a trace amount of halogen elements
(e.g., iodine or bromine) into an inert gas such as nitrogen or
argon. The introduction of halogen elements will help set the
temperature of the filament to a high value while suppressing
breakage of the filament. Thus, the halogen lamps HL have the
properties of having a longer life than typical incandescent lamps
and being able to apply intense light continuously. That is, the
halogen lamps HL are continuous lighting lamps that continuously
emit light for at least one second. The halogen lamps HL are also
long-life because of their rod-like shape, and when arranged in the
horizontal direction, exhibits excellent efficiency in the
radiation of the semiconductor wafer W located above the halogen
lamps.
As illustrated in FIG. 7, in both of the upper and lower rows, the
density of arrangement of the halogen lamps HL in a region that
faces the peripheral portion of the semiconductor wafer W held by
the holder 7 is higher than that in a region that faces the central
portion of the semiconductor wafer W. That is, in both of the upper
and lower rows, the halogen lamps HL in the peripheral portion of
the light source region are arranged at a shorter pitch than the
halogen lamps HL in the central portion. This increases the
illuminance of light from the peripheral portion of the light
source region rather than the illuminance of light from the central
portion, and thereby increases the amount of light applied to the
peripheral portion of the semiconductor wafer W where a temperature
drop is likely to occur, during heating using the light applied
from the halogen heater 4.
The halogen heater 4 also includes, within the casing 41, a
reflector 43 that is located under the two rows of halogen lamps HL
(FIG. 1). The reflector 43 reflects the light emitted from the
multiple halogen lamps HL toward the heat treatment space 65.
The louver 21 and the light-shielding member 25 are provided
between the halogen heater 4 and the holder 7. FIG. 8 is a
perspective view of the louver 21. The louver 21 is a cylindrical
(bottomless cylindrical) member with upper and lower opening ends.
The louver 21 is made of a material that is impervious to the light
emitted from the halogen lamps HL of the halogen heater 4, and for
example, made of opaque quartz with a large number of superfine air
bubbles contained in silica glass. The size of the louver 21 may be
appropriately changed in accordance with the configurations and
arrangement of the chamber 6 and the halogen heater 4. It is
sufficient that the outer diameter of the cylinder of the louver 21
be smaller than the area of the light source region in which the
halogen lamps HL are located. In the first preferred embodiment,
the louver 21 has an outer diameter of, for example, 300 mm, which
is the same as the diameter of the semiconductor wafer W, and an
inner diameter of, for example, 294 mm. The height of the louver 21
may be in the range of, for example, 15 to 25 mm (in the first
preferred embodiment, 16 mm).
As illustrated in FIG. 1, a louver stage 22 is provided on the top
of the casing 41 of the halogen heater 4. The louver stage 22 is a
flat plate-like member made of silica glass that is transparent to
the light emitted from the halogen lamps HL. The louver 21 is
disposed on the upper surface of the louver stage 22. The louver 21
is installed such that its cylinder has a central axis CX that
passes through the center of the semiconductor wafer W held by the
holder 7. The multiple halogen lamps HL of the halogen heater 4 are
arranged in the region that faces the lower surface of the
semiconductor wafer W held by the holder 7. Thus, the central axis
CX of the louver 21 also passes through the center of the array of
the halogen lamps HL.
When the cylindrical louver 21 made of opaque quartz is located
between the halogen heater 4 and the chamber 6 in this way, light
that travels from halogen lamps HL that are located outward of the
louver 21 toward an inner region of the semiconductor wafer W
(i.e., region that is inward of the peripheral portion), which
includes the vicinity of the central portion, will be blocked off
by the wall surface of the opaque louver 21 during light emission
from the multiple halogen lamps HL. On the other hand, light that
travels from the halogen lamps HL located outward of the louver 21
toward the peripheral portion of the semiconductor wafer W will not
be blocked. As a result, the presence of the louver 21 will help
reduce the amount of light travelling toward the inner region while
almost not reducing the amount of light travelling from the halogen
heater 4 toward the peripheral portion of the semiconductor wafer
W. That is, the heating of the inner region is weakened, and the
peripheral portion of the semiconductor wafer W where a temperature
drop is likely to occur is heated relatively strongly.
However, it is found that the installation of only the louver 21
above the halogen heater 4 will raise a new problem in that the
temperature of a region that is slightly inward of the peripheral
portion of the semiconductor wafer W is increased on the contrary
during light irradiation heating using the halogen lamps HL. FIG.
16 illustrates the in-plane temperature distribution of the
semiconductor wafer W in the presence of only the louver 21. The
radiation of light from the halogen lamps HL in the presence of
only the louver 21 may generate overheated regions (hot spots) 99
that have a higher temperature than the other regions, in areas
that are slightly inward of the peripheral portion of the
semiconductor wafer W, as illustrated in FIG. 16. For example, in
the case of the semiconductor wafer W having a diameter of 300 mm,
overheated regions 99 may appear around within a radius of about
117 mm in the surface of the semiconductor wafer W. That is, the
overheated regions 99 may have an arc shape having a diameter of
about 235 mm.
In view of this, the present invention provides the light-shielding
member 25, in addition to the louver 21, between the halogen heater
4 and the holder 7 in order to avoid the generation of such
arc-shaped overheated regions 99. FIG. 9 is a perspective view
illustrating the overall external appearance of the louver 21 and
the light-shielding member 25 according to the first preferred
embodiment. A ring stage 24 is installed on the top of the
cylindrical louver 21. The ring stage 24 is a disk-shaped member
made of silica glass that is transparent to the light emitted from
the halogen lamps HL. The ring stage 24 has a diameter that is the
same as the outer diameter of the louver 21 (in the present
embodiment, 300 mm). The ring stage 24 has a plate thickness of 2
to 3 mm.
The light-shielding member 25 is disposed on the upper surface of
the ring stage 24. That is, the light-shielding member 25 is
further disposed on the ring stage 24, which is a quartz plate
provided on the louver 21. The light-shielding member 25 has a
shape of a ring-shaped flat light-shielding ring having missing
portions. More specifically, the light-shielding member 25 has a
shape of a ring-shaped light-shielding ring having two cut-out
portions 29 at radially opposite positions. The outer diameter of
the ring portion of the light-shielding member 25 is smaller than
the inner diameter of the cylindrical louver 21, and may be 280 mm.
Thus, the outer size of the light-shielding member 25 is smaller
than the inner size of the louver 21. The inner diameter of the
ring portion of the light-shielding member 25 is, for example, 260
mm, and the plate thickness of the light-shielding member 25 is,
for example, 2 mm.
The light-shielding member 25 is made of a material that is
impervious to the light emitted from the halogen lamps HL of the
halogen heater 4, and may be made of opaque quartz with a large
number of superfine air bubbles contained in silica glass. That is,
the louver 21 and the light-shielding member 25 are made of the
same material.
The central axis CX of the louver 21 coincides with the central
axis of the ring portion of the light-shielding member 25. Thus,
the light-shielding member 25 is also installed such that its ring
portion has a central axis that passes through the center of the
semiconductor wafer W held by the holder 7.
Referring back to FIG. 1, the controller 3 controls the
above-described various operating mechanisms of the heat treatment
apparatus 1. The controller 3 has a similar hardware configuration
to that of a typical computer. That is, the controller 3 includes a
CPU that is a circuit for performing various types of computations,
a ROM that is a read-only memory for storing basic programs, a RAM
that is a readable/writable memory for storing various types of
information, and a magnetic disk for storing control software and
control data. The processing of the heat treatment apparatus 1 is
implemented by the CPU of the controller 3 executing predetermined
processing programs.
The heat treatment apparatus 1 also includes, in addition to the
above-described configuration, various cooling structures in order
to prevent an excessive temperature increase in the halogen heater
4, the flash heater 5, and the chamber 6 due to heat energy
generated by the halogen lamps HL and the flash lamps FL during the
heat treatment of the semiconductor wafer W. For example, the
chamber 6 may have a water-cooled tube (not shown) in the wall. The
halogen heater 4 and the flash heater 5 may have an air cooling
structure for exhausting heat by forming an internal flow of gas.
Moreover, air may be supplied to the spacing between the upper
chamber window 63 and the lamp-light irradiation window 53 to cool
the flash heater 5 and the upper chamber window 63.
Next is a description of the procedure of processing performed on
the semiconductor wafer W by the heat treatment apparatus 1. The
semiconductor wafer W to be processed here is a semiconductor
substrate that is doped with impurities (ions) by ion implantation.
These impurities are activated by flash light irradiation and heat
treatment (annealing) performed by the heat treatment apparatus 1.
The following procedure of processing performed by the heat
treatment apparatus 1 is implemented by the controller 3
controlling the operating mechanisms of the heat treatment
apparatus 1.
First, the valve 84 for supplying a gas and the valves 89 and 192
for exhausting a gas are opened to start the supply and exhaust of
gases into and from the chamber 6. When the valve 84 is open, a
nitrogen gas is supplied from the gas supply port 81 to the heat
treatment space 65. When the valve 89 is open, the gas in the
chamber 6 is exhausted from the gas exhaust port 86. Thereby, the
nitrogen gas supplied from the upper part of the heat treatment
space 65 in the chamber 6 flows downward and is exhausted from the
lower part of the heat treatment space 65.
When the valve 192 is open, the gas in the chamber 6 is also
exhausted from the transport opening 66. Moreover, the atmosphere
around the driving part of the transfer mechanism 10 is also
exhausted by an exhaust mechanism (not shown). During the heat
treatment of the semiconductor wafer W by the heat treatment
apparatus 1, the nitrogen gas continues to be supplied to the heat
treatment space 65, and the amount of the nitrogen gas supplied is
appropriately changed depending on the processing step.
Then, the gate valve 185 is opened to open the transport opening
66, and the ion-implanted semiconductor wafer W is transported into
the heat treatment space 65 of the chamber 6 through the transport
opening 66 by a transport robot located outside the apparatus. The
semiconductor wafer W transported into the heat treatment space 65
by the transport robot is moved to a position directly above the
holder 7 and stopped. Then, the pair of transfer arms 11 of the
transfer mechanism 10 move horizontally from the retracted
positions to the transfer operation positions and upward, so that
the lift pins 12 pass through the through holes 79 and protrude
from the upper surface of the holding plate 75 of the susceptor 74
to receive the semiconductor wafer W. At this time, the lift pins
12 are elevated to a position above the upper end of the substrate
support pins 77.
After the semiconductor wafer W is placed on the lift pins 12, the
transport robot is withdrawn from the heat treatment space 65, and
the transport opening 66 is closed by the gate valve 185. Then, the
pair of transfer arms 11 move downward so that the semiconductor
wafer W is transferred from the transfer mechanism 10 to the
susceptor 74 of the holder 7 and held in a horizontal position from
the underside. The semiconductor wafer W is supported by the
multiple substrate support pins 77 provided upright on the holding
plate 75 and held by the susceptor 74. The semiconductor wafer W is
held by the holder 7 such that its patterned and impurity-doped
front surface faces upward. A predetermined spacing is provided
between the rear surface (major surface opposite the front surface)
of the semiconductor wafer W supported by the multiple substrate
support pins 77 and the holding surface 75a of the holding plate
75. The pair of transfer arms 11 that have moved down to a position
below the susceptor 74 are retracted to their retracted position,
i.e., retracted to the inside of the recessed portion 62, by the
horizontal movement mechanism 13.
After the semiconductor wafer W is held in a horizontal position
from the underside by the susceptor 74 of the holder 7 made of
quartz, all of the 40 halogen lamps HL of the halogen heater 4 are
turned on in unison to start preheating (assist-heating). The
halogen light emitted from the halogen lamps HL passes through the
louver stage 22, the ring stage 24, the lower chamber window 64,
and the susceptor 74, which are made of quartz, and is radiated
from the rear surface (main surface on the opposite side to the
front surface) of the semiconductor wafer W. The semiconductor
wafer W that has received the light emitted from the halogen lamps
HL is preheated, and thereby the temperature of the semiconductor
wafer W rises. Note that the transfer arms 11 of the transfer
mechanism 10 that have retracted to the inside of the recessed
portion 62 will not impede the heating using the halogen lamps
HL.
During the preheating using the halogen lamps HL, the temperature
of the semiconductor wafer W is measured with the radiation
thermometer 120. That is, the radiation thermometer 120 receives
infrared light that is radiated from the rear surface of the
semiconductor wafer W held by the susceptor 74 through the opening
78, and measures the increasing wafer temperature. The measured
temperature of the semiconductor wafer W is transmitted to the
controller 3. The controller 3 controls the output of the halogen
lamps HL while monitoring whether the temperature of the
semiconductor wafer W, which is rising by the radiation of light
from the halogen lamps HL, has reached a predetermined preheating
temperature T1. That is, the controller 3 performs feedback control
of the output of the halogen lamps HL on the basis of the measured
value obtained by the radiation thermometer 120, so that the
temperature of the semiconductor wafer W will reach the preheating
temperature T1. The preheating temperature T1 is set to a range of
about 200.degree. C. to 800.degree. C. at which the impurities
doped in the semiconductor wafer W will not be diffused by heat,
and preferably, a range of about 350.degree. C. to 600.degree. C.
(in the present preferred embodiment, 600.degree. C.).
In the first preferred embodiment, the opaque cylindrical louver 21
and the ring-shaped light-shielding member 25 having missing
portions at radially opposite positions are provided between the
halogen heater 4 and the chamber 6 so as to block off part of the
light travelling from the halogen heater 4 toward the semiconductor
wafer W held by the holder 7. A description will now be given of
how light is shielded in the case where a perfect ring-shaped
light-shielding member 251 that includes no cut-out portions 29 is
provided, instead of the above-described light-shielding member 25.
FIG. 10 is a perspective view of the overall external appearance of
the cylindrical louver 21 that includes the perfect ring-shaped
light-shielding member 251. The light-shielding member 25 of the
present preferred embodiment illustrated in FIG. 9 is obtained by
forming the cut-out portions 29 at the radially opposite positions
of the perfect ring-shaped light-shielding member 251 in FIG. 10.
FIG. 11 illustrates how light is shielded by the structure of FIG.
10. As described above, in the present preferred embodiment, the
multiple halogen lamps HL are arranged in the region larger than
the main surface of the disk-shaped semiconductor wafer W, and the
outer diameter of the louver 21 is the same as the diameter of the
semiconductor wafer W. Thus, some halogen lamps HL are located
outward of the cylindrical louver 21. As illustrated in FIG. 11,
part of the light that is emitted from the halogen lamps HL located
outward of the louver 21 toward the semiconductor wafer W is
blocked off by the opaque louver 21.
The central axis of the ring-shaped light-shielding member 251
coincides with the central axis CX of the louver 21, and the outer
diameter of the light-shielding member 251 is smaller than the
inner diameter of the louver 21. Thus, there is clearance that
allows the light emitted from the halogen lamps HL to pass through
it, between the inner wall surface of the louver 21 and the outer
circumference of the light-shielding member 251. The light that has
been emitted from the halogen lamps HL and passed through the
clearance created between the inner wall surface of the louver 21
and the outer circumference of the light-shielding member 251 is
radiated to the peripheral portion of the semiconductor wafer W
held by the holder 7. This radiation of light from the halogen
lamps HL relatively increases the illuminance in the peripheral
portion of the semiconductor wafer W, and accordingly the
peripheral portion where a temperature drop is likely to occur is
heated strongly.
On the other hand, the opaque annular light-shielding member 251,
which has an outer diameter of 280 mm and an inner diameter of 260
mm, is located below a region that is slightly inward of the
peripheral portion of the semiconductor wafer W held by the holder
7, i.e., below the overheated regions 99 in FIG. 16 that might be
generated in the presence of only the louver 21. Thus, light that
is emitted from the halogen lamps HL and travels toward the
overheated regions 99 that are slightly inward of the peripheral
portion of the semiconductor wafer W will be blocked off by the
light-shielding member 251. This relatively reduces the illuminance
in the overheated regions 99 of the semiconductor wafer W that
might be generated in the presence of only the louver 21, and
weakens the heating of the overheated regions 99.
However, as illustrated in FIG. 11, the perfect ring-shaped
light-shielding member 251 will also block off the light that
should originally be applied to a shadow region SA of the
semiconductor wafer W, the shadow region SA being a region
generated as a result of the louver 21 blocking off part of the
light travelling from the halogen lamps HL located outward of the
louver 21 toward the semiconductor wafer W. That is, the
light-shielding member 251 blocks off the light that should
originally travel from the halogen lamps HL located inward of the
louver 21 toward the shadow region SA. Note that whether or not the
shadow region SA appears in the semiconductor wafer W, as a result
of the louver 21 blocking off the light travelling from the halogen
lamps HL located outward of the louver 21, depends on the relative
positions of the halogen lamps HL, the louver 21, and the
semiconductor wafer W. In the case of the positional relationship
according to the present preferred embodiment, the shadow region SA
will appear as a result of the louver 21 blocking off the light
travelling from the outer halogen lamps HL in the lower row of the
halogen heater 4, but no shadow regions SA will appear due to the
outer halogen lamps HL in the upper row.
The shadow region SA of the semiconductor wafer W where less light
reaches from the halogen lamps HL is a low-temperature region (cold
spot) that has a lower temperature than the other regions. In the
presence of such cold spots, the in-plane temperature distribution
of the semiconductor wafer W becomes uneven during flash heating
using the flash lamps FL, and degradation of the semiconductor
device characterizes and a decrease in yield are of concern.
In view of this, the light-shielding member 25 according to the
present invention is a ring-shaped light-shielding ring
(light-shielding member 251) having the cut-out portions 29 at the
radially opposite positions. FIG. 12 illustrates how optical paths
are adjusted by the louver 21 and the light-shielding member 25
according to the first preferred embodiment. FIG. 12 is a side view
of an area where the cut-out portions 29 in FIG. 9 are formed.
As illustrated in FIG. 12, in the presence of the light-shielding
member 25 with the cut-out portions 29, the light emitted from the
halogen lamps HL located inward of the louver 21 will pass through
the cut-out portions 29 and reach the shadow region SA of the
semiconductor wafer W. That is, the presence of the cut-out
portions 29 of the light-shielding member 25 allows light to reach
the shadow region SA of the semiconductor wafer W that is shielded
from the light emitted from the halogen lamps HL by the louver 21.
As a result, the illuminance in the shadow region SA is relatively
increased, and the shadow region SA is heated in the same manner as
the other regions. Because the shadow region SA appears as a result
of the louver 21 blocking off the light emitted from the outer
halogen lamps HL in the lower row of the halogen heater 4, the
cut-out portions 29 are formed at such positions that allow light
to reach the shadow region SA that appears as a result of the light
from the outer halogen lamps HL in the lower row being blocked
off.
In this way, the combination of the louver 21 and the
light-shielding member 25 with the cut-out portions 29 will
effectively resolve the problem of unevenness in the in-plane
temperature distribution of the semiconductor wafer W during light
irradiation using the halogen lamps HL.
After the temperature of the semiconductor wafer W has reached the
preheating temperature T1 and a predetermined period of time has
elapsed, the flash lamps FL of the flash heater 5 emit flash light
to the front surface of the semiconductor wafer W. At this time,
part of the flash light emitted from the flash lamps FL travels
directly into the chamber 6, and part of the flash light is once
reflected by the reflector 52 and then travels into the chamber 6.
Thus, flash heating of the semiconductor wafer W is implemented by
this application of flash light.
Flash heating, which is implemented by the application of flash
light (flashes) from the flash lamps FL, can raise the front
surface temperature of the semiconductor wafer W in a short time.
That is, the flash light emitted from the flash lamps FL is an
extremely short, strong flash of light that is obtained by
converting the electrostatic energy stored in advance in the
capacitor into an extremely short optical pulse and whose
irradiation time is approximately in the range of 0.1 to 100
milliseconds. The front surface temperature of the semiconductor
wafer W that is heated with the flash light emitted from the flash
lamps FL will rise instantaneously to a processing temperature T2
of 1000.degree. C. or higher and then drop rapidly after the
impurities doped in the semiconductor wafer W are activated. In
this way, the heat treatment apparatus 1 can raise and drop the
front surface temperature of the semiconductor wafer W in an
extremely short time, and therefore can activate the impurities
doped in the semiconductor wafer W while suppressing the diffusion
of the impurities due to heat. Since the time necessary to activate
impurities is extremely shorter than the time necessary to diffuse
impurities with heat, the activation of impurities will be
completed in such a short time (e.g., about 0.1 to 100
milliseconds) that does not cause diffusion.
In the first preferred embodiment, the combination of the louver 21
and the light-shielding member 25 having the cut-out portions 29
will help make uniform the in-plane temperature distribution of the
semiconductor wafer W in the stage of preheating by the halogen
heater 4 and accordingly make uniform the in-plane temperature
distribution of the semiconductor wafer W surface during flash
light irradiation.
After the flash heating ends and a predetermined period of time has
elapsed, the halogen lamps HL are turned off. The temperature of
the semiconductor wafer W thus rapidly drops from the preheating
temperature T1. The decreasing temperature of the semiconductor
wafer W is measured with the radiation thermometer 120, and the
measurement result is transmitted to the controller 3. The
controller 3 monitors the measurement result to determine whether
the temperature of the semiconductor wafer W has dropped to a
predetermined temperature. After the temperature of the
semiconductor wafer W has dropped to the predetermined temperature
or lower, the pair of transfer arms 11 of the transfer mechanism 10
move horizontally from the retracted positions to the transfer
operation positions and upward again, so that the lift pins 12
protrude from the upper surface of the susceptor 74 and receive the
heat-treated semiconductor wafer W from the susceptor 74. Then, the
transport opening 66 that has been closed by the gate valve 185 is
opened, and the semiconductor wafer W placed on the lift pins 12 is
transported out of the apparatus by the transport robot. This
completes the heat treatment of the semiconductor wafer W in the
heat treatment apparatus 1.
In the first preferred embodiment, the opaque cylindrical louver 21
and the light-shielding member 25, which is a ring-shaped
light-shielding ring having the cut-out portions 29, are provided
between the halogen heater 4 and the chamber 6 so as to adjust the
optical paths of light travelling from the halogen heater 4 toward
the semiconductor wafer W held by the holder 7. As described
previously, in the presence of only the louver 21 and the perfect
ring-shaped light-shielding member, the shadow region SA where less
light reaches from the halogen lamps HL is likely to appear in the
semiconductor wafer W, and accordingly the in-plane temperature
distribution tends to become uneven. In view of this, the
light-shielding member 25 obtained by forming the cut-out portions
29 in the perfect ring shape is provided to allow the light emitted
from the halogen lamps HL located inward of the louver 21 to reach
the shadow region SA, and to thereby make uniform the in-plane
temperature distribution of the semiconductor wafer W during
preheating. As a result, the in-plane temperature distribution of
the semiconductor wafer W during flash heating can also be made
uniform.
Second Preferred Embodiment
Next, a second preferred embodiment according to the present
invention will be described. The overall configuration of the heat
treatment apparatus according to the second preferred embodiment is
generally similar to that described in the first preferred
embodiment. The procedure of processing performed on the
semiconductor wafer W according to the second preferred embodiment
is also the same as that described in the first preferred
embodiment. The second preferred embodiment differs from the first
preferred embodiment in that the light-shielding member has
transparent portions, instead of cut-out portions.
FIG. 13 is a plan view of a light-shielding member 125 according to
the second preferred embodiment. While the light-shielding member
25 of the first preferred embodiment is a ring-shaped
light-shielding ring having the cut-out portions 29, the
light-shielding member 125 of the second preferred embodiment is a
ring-shaped light-shielding ring, part of which is made of a member
that is transparent to the light emitted from the halogen lamps HL.
That is, the light-shielding member 125 of the second preferred
embodiment includes a transparent portion 122, which forms part of
the ring-shaped flat-plate ring, and an opaque portion 121, which
is the remaining part of the ring. The transparent portion 122 is
made of, for example, transparent quartz that allows the light
emitted from the halogen lamps HL to pass through it, and the
opaque portion 121 is made of, for example, opaque quartz similar
to that used in the first preferred embodiment. The transparent
portion 122 of transparent quartz and the opaque portion 121 of
opaque quartz may be bonded to each other by welding. A bonded unit
of the opaque portion 121 and the transparent portion 122 has a
perfect ring shape. Such a ring-shaped unit may have two
transparent portions 122 at radially opposite positions. In other
words, the light-shielding member 125 of the second preferred
embodiment is obtained by replacing the cut-out portions 29 of the
light-shielding member 25 of the first preferred embodiment with
transparent quartz.
The size of the light-shielding member 125 is the same as that of
the first preferred embodiment, and may have an outer diameter of
280 mm, an inner diameter of 260 mm, and a thickness of 2 mm. This
light-shielding member 125 is placed on the upper surface of the
ring stage 24 provided at the top of the cylindrical louver 21. The
rest of the configuration of the second preferred embodiment,
excluding the form of the light-shielding member 125, is the same
as that described in the first preferred embodiment.
When, in the second preferred embodiment, the semiconductor wafer W
is preheated by the application of light from the halogen heater 4,
the light emitted from the halogen lamps HL located inward of the
louver 21 will pass through the transparent portions 122, which
form part of the light-shielding member 125, and reach the shadow
region SA of the semiconductor wafer W. That is, the presence of
the transparent portions 122 of the light-shielding member 125 will
help light reach the shadow region SA of the semiconductor wafer W
that is shielded from the light emitted from the halogen lamps HL
by the louver 21. Accordingly, the illuminance in the shadow region
SA is relatively increased, and the shadow region SA is heated in
the same manner as the other regions. This will help make uniform
the in-plane temperature distribution of the semiconductor wafer W
during preheating and consequently make uniform the in-plane
temperature distribution of the semiconductor wafer W during flash
heating.
Third Preferred Embodiment
Next, a third preferred embodiment of the present invention will be
described. The overall configuration of a heat treatment apparatus
according to the third preferred embodiment is generally similar to
that described in the first preferred embodiment. The procedure of
processing performed on the semiconductor wafer W according to the
third preferred embodiment is also the same as that described in
the first preferred embodiment. The third preferred embodiment
differs from the first preferred embodiment in the shape of a
light-shielding member.
FIG. 14 is a plan view of a light-shielding member 225 according to
the third preferred embodiment. The light-shielding member 225 of
the third preferred embodiment is configured by multiple
light-shieling parts, with four plate-like light-shielding pieces
222 arranged inside a light-shielding ring 221 having cut-out
portions 229. The light-shielding ring 221 and the four
light-shielding pieces 222, which constitute the light-shielding
member 225, are made of a material that is impervious to the light
emitted from the halogen lamps HL of the halogen heater 4, and may
be made of opaque quartz with a large number of superfine air
bubbles contained in silica glass.
The light-shielding ring 221 is similar to the light-shielding
member 25 of the first preferred embodiment. That is, the shape of
the light-shielding ring 221 is a ring shape having two cut-out
portions 229 at radially opposite positions. The outer diameter of
the light-shielding ring 221 is smaller than the inner diameter of
the cylindrical louver 21. Each light-shielding piece 222 is a
rectangular plate-like member of such a size that can be housed
inside the light-shielding ring 221. The light-shielding ring 221
and the four light-shielding pieces 222 are placed in the form of
arrangement as illustrated in FIG. 14 on the ring stage 24 provided
at the top of the cylindrical louver 21. The rest of the
configuration of the third preferred embodiment, excluding the
shape of the light-shielding member 225, is the same as that
described in the first preferred embodiment.
When, in the third preferred embodiment, the semiconductor wafer W
is preheated by the application of light from the halogen heater 4,
the light emitted from the halogen lamps HL located inward of the
louver 21 will pass through the cut-out portions 229, which form
part of the light-shielding member 225, and reach the shadow region
SA of the semiconductor wafer W. That is, the presence of the
cut-out portions 229 of the light-shielding member 225 will help
light reach the shadow region SA of the semiconductor wafer W that
is shielded from the light emitted from the halogen lamps HL by the
louver 21. Accordingly, the illuminance in the shadow region SA is
relatively increased, and the shadow region SA is heated in the
same manner as the other regions. This will help make uniform the
in-plane temperature distribution of the semiconductor wafer W
during preheating and consequently make uniform the in-plane
temperature distribution of the semiconductor wafer W during flash
heating.
In the case where, when preheating using the halogen heater 4 is
performed in the presence of only the louver 21, additional
overheated regions, in addition to the overheated regions 99 of a
shape illustrated in FIG. 16, appear inside the overheated regions
99 in the surface of the semiconductor wafer W, the light-shielding
pieces 222 may be provided, in addition to the light-shielding ring
221, as in the third preferred embodiment. This configuration will
help individually block off the light travelling toward the
overheated regions and accordingly effectively make uniform the
in-plane temperature distribution of the semiconductor wafer W.
Fourth Preferred Embodiment
Next, a fourth preferred embodiment according to the present
invention will be described. The overall configuration of a heat
treatment apparatus according to the fourth preferred embodiment is
generally similar to that described in the first preferred
embodiment. The procedure of processing performed on the
semiconductor wafer W according to the fourth preferred embodiment
is also the same as that described in the first preferred
embodiment. The fourth preferred embodiment differs from the first
preferred embodiment in the shape of a light-shielding member.
FIG. 15 is a plan view of a light-shielding member 325 according to
the fourth preferred embodiment. The light-shielding member 325 of
the fourth preferred embodiment is constituted by multiple
light-shieling parts, with a plate-like light-shielding piece 322
arranged inside a flat square frame-like light-shielding frame 321
having cut-out portions 329. The light-shielding frame 321 and the
light-shielding piece 322, which constitute the light-shielding
member 325, are made of a material that is impervious to the light
emitted from the halogen lamps HL of the halogen heater 4, and may
be made of opaque quartz with a large number of superfine air
bubbles contained in silica glass.
The diagonal line of the light-shielding frame 321 having a square
frame-like shape has a length that is smaller than the inner
diameter of the cylindrical louver 21. The shape of the
light-shielding frame 321 is obtained by forming the cut-out
portions 329 at the centers of two opposite sides among the four
sides of the square. The light-shielding piece 322 is a circulate
plate-like member having a size that can be housed in the
light-shielding frame 321. The light-shielding frame 321 and the
light-shielding piece 322 are placed in the form of arrangement as
illustrated in FIG. 15 on the upper surface of the ring stage 24
provided at the top of the cylindrical louver 21. The rest of the
configuration of the fourth preferred embodiment, excluding the
shape of the light-shielding member 325, is the same as that
described in the first preferred embodiment.
When, in the fourth preferred embodiment, the semiconductor wafer W
is preheated by the application of light from the halogen heater 4,
the light emitted from the halogen lamps HL located inward of the
louver 21 will pass through the cut-out portions 329 of the
light-shielding member 325 and reach the shadow region SA of the
semiconductor wafer W. That is, the presence of the cut-out
portions 329 of the light-shielding member 325 will help light
reach the shadow region SA of the semiconductor wafer W that is
shielded from the light emitted from the halogen lamps HL by the
louver 21. Accordingly, the illuminance in the shadow region SA is
relatively increased, and the shadow region SA is heated in the
same manner as the other regions. This will help make uniform the
in-plane temperature distribution of the semiconductor wafer W
during preheating and consequently make uniform the in-plane
temperature distribution of the semiconductor wafer W during flash
heating.
In the case where, when preheating using the halogen heater 4 is
performed in the presence of only the louver 21, additional
overheated regions, in addition to the overheated regions 99 of a
shape illustrated in FIG. 16, appear inside the overheated regions
99 in the surface of the semiconductor wafer W, the light-shielding
piece 322 may be provided, in addition to the light-shielding frame
321, as in the fourth preferred embodiment. This configuration will
help individually block off the light travelling toward the
overheated regions and accordingly effectively make uniform the
in-plane temperature distribution of the semiconductor wafer W.
Variations
While the above has been a description of preferred embodiments of
the present invention, various modifications other than the
examples described above are possible without departing from the
scope of the invention. For example, while in the above-described
preferred embodiments, the light-shielding members 25, 225, and 325
and the opaque portions 121 of the light-shielding member 125 are
made of opaque quartz with a large number of superfine air bubbles
contained in silica glass, the material for these members is not
limited to opaque quartz. For example, the light-shielding members
25, 225, and 325 and the opaque portions 121 of the light-shielding
member 125 may be made of a material, such as ceramic or metal,
that is impervious to the light emitted from the halogen lamps HL
of the halogen heater 4. Opaque materials do not necessarily have
to be completely opaque materials (with 0% transmittance), and may
be materials that have transmittance of 15% or less with respect to
the light emitted from the halogen lamps HL.
The louver 21 and the light-shielding members 25, 125, 225, and 325
may be made of different materials as long as the materials are
impervious to the light emitted from the halogen lamps HL. In the
third preferred embodiment, the light-shielding ring 221 and the
multiple light-shielding pieces 222 may be made of different
materials. In this case, each light-shielding piece 222 may have
different transmittance with respect to the light emitted from the
halogen lamps HL. If overheated regions generated in the surface of
the semiconductor wafer W have varying temperatures as a result of
preheating in the presence of only the louver 21, the multiple
light-shielding pieces 222 may preferably have different
transmittance depending on the temperatures of the overheated
regions. More specifically, the transmittance of a light-shielding
piece 222 that corresponds to an overheated region having a much
higher temperature than the other regions may be preferably set to
low (as close as 0% transmittance), whereas the transmittance of a
light-shielding piece 222 that corresponds to an overheated region
having a slightly higher temperature than the other regions may be
preferably set to high. In this case, the illuminance in the
overheated regions can be adjusted with higher accuracy, and the
in-plane temperature distribution of the semiconductor wafer W can
be made uniform effectively. In the third preferred embodiment, the
light-shielding ring 221 and the multiple light-shielding pieces
222 may of course have different transmittance.
Similarly, the light-shielding frame 321 and the light-shielding
piece 322 of the fourth preferred embodiment may be made of
different materials. In this case, the light-shielding frame 321
and the light-shielding piece 322 may have different transmittance
with respect to the light emitted from the halogen lamps HL.
Also, the shape of the light-shielding member and the number of
parts thereof are not limited to the examples described in the
first to fourth preferred embodiments. For example, the
light-shielding member may have an ellipsoidal shape, a star shape,
or a polygonal shape rather than the circular shape. The number of
parts of the light-shielding members may be changed appropriately.
If the light-shielding members include multiples parts, these parts
may be arranged symmetrically or asymmetrically depending on the
distribution of overheated regions in the surface of the
semiconductor wafer W.
The cut-out portions 229 of the third preferred embodiment and the
cut-out portions 329 of the fourth preferred embodiment may be
replaced by transparent portions as in the second preferred
embodiment. In short, part of the light-shielding members may be
either removed, or made transparent by increasing the
transmittance.
While in the above-described preferred embodiments, the shadow
region SA appears in the semiconductor wafer W as a result of the
louver 21 blocking off the light travelling from the outer halogen
lamps HL in the lower row of the halogen heater 4, the shadow
region SA may appear, depending on the arrangement of the halogen
lamps HL or other constituent elements, due to the presence of the
outer halogen lamps HL in the upper row. In this case, cut-out
portions may be formed at radially opposite positions in a
direction that is orthogonal to the diameter across which the
cut-out portions 29 are formed in the above-described preferred
embodiments. Even in such a case, the light emitted from the
halogen lamps HL located inward of the louver 21 will pass through
the cut-out portions and reach the shadow region SA of the
semiconductor wafer W. Thus, the in-plane temperature distribution
of the semiconductor wafer W can be made uniform as in the
above-described preferred embodiments. In summary, the cut-out
portions (or transparent portions) of a light-shielding member may
be provided so as to allow light to reach the shadow region SA of
the semiconductor wafer W that is shielded from the light emitted
from the halogen heater 4 by the opaque cylindrical louver 21.
While in the above-described preferred embodiments, the flash
heater 5 includes 30 flash lamps FL, the present invention is not
limited to this example, and the flash heater 5 may include an
arbitrary number of flash lamps FL. The flash lamps FL are not
limited to xenon flash lamps, and may be krypton flash lamps. The
number of halogen lamps HL included in the halogen heater 4 is also
not limited to 40, and the halogen heater 4 may include an
arbitrary number of halogen lamps HL as long as each of the upper
and lower rows includes an array of multiple halogen lamps.
Substrates to be processed by the heat treatment apparatus
according to the present invention are not limited to semiconductor
wafers, and may be glass substrates for use in flat panel displays
such as liquid crystal displays, or may be substrates for solar
cells. The technique according to the present invention is also
applicable to other applications such as heat treatment of a high
dielectric gate insulating film (High-k film), bonding of metal and
silicon, and crystallization of polysilicon.
The application of the heat treatment technique according to the
present invention is not limited to flash-lamp annealing
apparatuses, and this technique is also applicable to, for example,
lamp annealing apparatuses using halogen lamps or apparatuses, such
as CVD apparatuses, that use different heat sources other than
flash lamps. In particular, the technique of the present invention
is preferably applicable to backside annealing apparatuses in which
halogen lamps are located below a chamber and heat treatment is
performed with the light emitted from the rear surface of the
semiconductor wafer.
While the invention has been shown and described in detail, the
foregoing description is in all aspects illustrative and not
restrictive. It is therefore to be understood that numerous
modifications and variations can be devised without departing from
the scope of the invention.
* * * * *